Move Alsa device opening into the audio thread, and add in support for multi-channel audio.

Moving the device opening into the audio thread will prevent browser hangs for badly behaving alsa implementations (like pulseaudio) that can hang snd_pcm_open if pulseaudiod is wedged, even if SND_PCM_NONBLOCK is requested.

For multi-channel audio, device enumeration has been added to try and find a multi-channel device with a stable channel mapping.  According to http://0pointer.de/blog/projects/guide-to-sound-apis.html, default should only be used with mono and stereo stream because the channel ordering is not defined by Alsa. To get a well-defined channel ordering, one must use one of the surround40, surround51, etc., device names.  However, these device names do not always allow multiple opens, so a fallback scheme is implemented to use default if necessary.

BUG=20945,17703
TEST=listened with built-in soundcard and USB soundcard with various other audio programs running.

Review URL: http://codereview.chromium.org/275022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@29299 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 12 insertions, 0 deletions

diff --git a/media/audio/linux/alsa_wrapper.cc b/media/audio/linux/alsa_wrapper.cc
index 8463686..303a1f1 100644
--- a/media/audio/linux/alsa_wrapper.cc
+++ b/media/audio/linux/alsa_wrapper.cc
@@ -17,6 +17,18 @@ int AlsaWrapper::PcmOpen(snd_pcm_t** handle, const char* name,
   return snd_pcm_open(handle, name, stream, mode);
 }
 
+int AlsaWrapper::DeviceNameHint(int card, const char* iface, void*** hints) {
+  return snd_device_name_hint(card, iface, hints);
+}
+
+char* AlsaWrapper::DeviceNameGetHint(const void* hint, const char* id) {
+  return snd_device_name_get_hint(hint, id);
+}
+
+int AlsaWrapper::DeviceNameFreeHint(void** hints) {
+  return snd_device_name_free_hint(hints);
+}
+
 int AlsaWrapper::PcmClose(snd_pcm_t* handle) {
   return snd_pcm_close(handle);
 }